Galvanically Isolated Current Sensor in Power Module Substrate
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Solution Overview
Problem
The integration of magnetoresistive or Hall sensors in power modules for measuring load current is challenging due to the need for precise positioning and galvanic isolation, which increases production complexity and requires additional ceramic structures for thermal and power cycling reliability.
Innovation Solution
A power module design with a semiconductor die interposed between two metallized ceramic substrates, where the sensor is galvanically isolated from one substrate and aligned with a metal region on the other, allowing for double-sided cooling and reduced thermal resistance without additional isolating structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistive or Hall sensors are integrated in a power module for measuring load current, then current sensing capability is achieved, but production complexity increases due to the need for additional ceramic isolating structures
Solution Approach 1:
The sensor is integrated directly into the power module substrate, merging the sensing function with the existing module structure. This eliminates the need for separate ceramic isolating structures while maintaining galvanic isolation through the substrate design itself, thereby reducing production complexity while preserving current sensing capability
2Reliability
If additional ceramic isolating structures are added for galvanic isolation, then reliability under thermal stress is improved, but device complexity and production difficulty increase
Solution Approach 1:
The power module substrate serves multiple functions simultaneously: it provides mechanical support, electrical connections, thermal management pathways, and galvanic isolation for the sensor. This multi-functionality eliminates the need for dedicated ceramic isolating structures while maintaining reliability under thermal stress through the substrate's inherent properties and design
3Measurement precision
If the sensor is placed in the correct position for accurate measurement, then measurement precision is improved, but positioning difficulty and production complexity increase
Solution Approach 1:
The sensor mounting position is pre-configured during substrate fabrication with precise alignment features and reference marks. This preliminary positioning preparation ensures that during assembly, the sensor can be accurately placed relative to the current-carrying conductors without requiring complex real-time alignment procedures, thereby maintaining measurement precision while simplifying production
4Reliability
If galvanic isolation is achieved through additional ceramic structures, then electrical isolation is improved, but thermal resistance increases and power density decreases
Solution Approach 1:
The galvanic isolation function is integrated into the substrate design itself rather than requiring separate ceramic structures. This allows thermal pathways to remain continuous through the substrate while the sensor maintains electrical isolation through the substrate's inherent insulating properties or design features, thereby reducing thermal resistance and increasing power density while preserving galvanic isolation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the module's thermal performance, increases power density, and simplifies production by eliminating the need for extra isolating structures, while maintaining accurate current sensing.
Implementation Method 1
the sensor is aligned with a first metal region of the metallized side of the second substrate so that the sensor can measure a magnetic field generated by the first metal region
Implementation Method 2
The integration of magnetoresistive or Hall sensors in a power module for measuring load current
Data Source
AI summary
A method of sensing current flowing in a power module is provided. The module includes a first substrate having a metallized side, a second substrate spaced apart from the first substrate and having a metallized side facing the metallized side of the first substrate, and a semiconductor die interposed between the first and second substrates. The semiconductor die has a first side connected to the metallized side of the first substrate and an opposing second side connected to the metallized side of the second substrate. The module further includes a sensor connected to the metallized side of the first substrate and galvanically isolated from the metallized side of the second substrate. The sensor is aligned with a first metal region of the metallized side of the second substrate, for measuring a magnetic field generated by the first metal region responsive to the current flowing through the first metal region.